mirror of https://gitee.com/bigwinds/arangodb
181 lines
7.3 KiB
JavaScript
181 lines
7.3 KiB
JavaScript
////////////////////////////////////////////////////////////////////////////////
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/// @brief query explain actions
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///
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/// @file
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///
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/// DISCLAIMER
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///
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/// Copyright 2012 triagens GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is triAGENS GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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/// @author Copyright 2012, triAGENS GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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/// @addtogroup ArangoAPI
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/// @{
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////////////////////////////////////////////////////////////////////////////////
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// -----------------------------------------------------------------------------
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// --SECTION-- global variables
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// -----------------------------------------------------------------------------
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var actions = require("org/arangodb/actions");
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////////////////////////////////////////////////////////////////////////////////
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/// @brief explain a query and return information about it
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///
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/// @RESTHEADER{POST /_api/explain,explains a query}
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///
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/// @REST{POST /_api/explain}
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///
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/// To explain how an AQL query would be executed on the server, the query string
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/// can be sent to the server via an HTTP POST request. The server will then validate
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/// the query and create an execution plan for it, but will not execute it.
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///
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/// The execution plan that is returned by the server can be used to estimate the
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/// probable performance of an AQL query. Though the actual performance will depend
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/// on many different factors, the execution plan normally can give some good hint
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/// on the amount of work the server needs to do in order to actually run the query.
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///
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/// The query string needs to be passed in the attribute @LIT{query} of a JSON
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/// object as the body of the POST request. If the query references any bind
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/// variables, these must also be passed in the attribute @LIT{bindVars}.
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///
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/// If the query is valid, the server will respond with @LIT{HTTP 200} and
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/// return a list of the individual query execution steps in the @LIT{"plan"}
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/// attribute of the response.
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///
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/// The server will respond with @LIT{HTTP 400} in case of a malformed request,
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/// or if the query contains a parse error. The body of the response will
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/// contain the error details embedded in a JSON object.
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/// Omitting bind variables if the query references any will result also result
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/// in an @LIT{HTTP 400} error.
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///
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/// @EXAMPLES
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///
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/// Valid query:
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///
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/// @verbinclude api-explain-valid
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///
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/// Invalid query:
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///
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/// @verbinclude api-explain-invalid
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///
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/// The data returned in the @LIT{plan} attribute of the result contains one
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/// element per AQL top-level statement (i.e. @LIT{FOR}, @LIT{RETURN},
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/// @LIT{FILTER} etc.). If the query optimiser removed some unnecessary statements,
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/// the result might also contain less elements than there were top-level
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/// statements in the AQL query.
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/// The following example shows a query with a non-sensible filter condition that
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/// the optimiser has removed so that there are less top-level statements:
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///
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/// @verbinclude api-explain-empty
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///
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/// The top-level statements will appear in the result in the same order in which
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/// they have been used in the original query. Each result element has at most the
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/// following attributes:
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/// - @LIT{id}: the row number of the top-level statement, starting at 1
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/// - @LIT{type}: the type of the top-level statement (e.g. @LIT{for}, @LIT{return} ...)
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/// - @LIT{loopLevel}: the nesting level of the top-level statement, starting at 1
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/// Depending on the type of top-level statement, there might be other attributes
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/// providing additional information, for example, if and which indexed will be
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/// used.
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/// Many top-level statements will provide an @LIT{expression} attribute that
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/// contains data about the expression they operate on. This is true for @LIT{FOR},
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/// @LIT{FILTER}, @LIT{SORT}, @LIT{COLLECT}, and @LIT{RETURN} statements. The
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/// @LIT{expression} attribute has the following sub-attributes:
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/// - @LIT{type}: the type of the expression. Some possible values are:
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/// - @LIT{collection}: an iteration over documents from a collection. The
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/// @LIT{value} attribute will then contain the collection name. The @LIT{extra}
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/// attribute will contain information about if and which index is used when
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/// accessing the documents from the collection. If no index is used, the
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/// @LIT{accessType} sub-attribute of the @LIT{extra} attribute will have the
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/// value @LIT{all}, otherwise it will be @LIT{index}.
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/// - @LIT{list}: a list of dynamic values. The @LIT{value} attribute will contain the
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/// list elements.
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/// - @LIT{const list}: a list of constant values. The @LIT{value} attribute will contain the
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/// list elements.
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/// - @LIT{reference}: a reference to another variable. The @LIT{value} attribute
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/// will contain the name of the variable that is referenced.
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///
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/// Please note that the structure of the explain result data might change in future
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/// versions of ArangoDB without further notice and without maintaining backwards
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/// compatibility.
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////////////////////////////////////////////////////////////////////////////////
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function POST_api_explain (req, res) {
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if (req.suffix.length != 0) {
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actions.resultNotFound(req, res, actions.ERROR_HTTP_NOT_FOUND);
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return;
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}
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var json = actions.getJsonBody(req, res);
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if (json === undefined) {
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return;
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}
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var result = AHUACATL_EXPLAIN(json.query, json.bindVars);
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if (result instanceof ArangoError) {
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actions.resultBad(req, res, result.errorNum, result.errorMessage);
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return;
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}
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result = { "plan" : result };
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actions.resultOk(req, res, actions.HTTP_OK, result);
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- initialiser
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// -----------------------------------------------------------------------------
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////////////////////////////////////////////////////////////////////////////////
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/// @brief explain gateway
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////////////////////////////////////////////////////////////////////////////////
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actions.defineHttp({
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url : "_api/explain",
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context : "api",
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callback : function (req, res) {
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try {
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switch (req.requestType) {
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case (actions.POST) :
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POST_api_explain(req, res);
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break;
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default:
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actions.resultUnsupported(req, res);
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}
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}
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catch (err) {
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actions.resultException(req, res, err);
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}
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}
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});
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////////////////////////////////////////////////////////////////////////////////
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/// @}
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////////////////////////////////////////////////////////////////////////////////
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// Local Variables:
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// mode: outline-minor
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// outline-regexp: "^\\(/// @brief\\|/// @addtogroup\\|// --SECTION--\\|/// @page\\|/// @}\\)"
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// End:
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